Self-locking cartridge case for fixed ammunition



June 13, 1961 c w. MUSSER 2,987,965

SELF-LOCKING CARTRIDGE CASE FOR FIXED AMMUNITION Filed Match 17, 1958 2 Sheets-Sheet 1 June 13, 1961 c w, ss 2,987,965

SELF-LOCKING CARTRIDGE CASE FOR FIXED AMMUNITION Filed March 17, 1958 2 Sheets-Sheet 2 INVENTOR. C WALTON MUSSER w. mm/w States C Walton Musser, Beverly, Mass., assignor to the United States of America as represented by the Secretary of the Army Filed Mar. 17, 1958, Ser. No. 722,108 4 Claims. (Cl. 891.7) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to weapons and particularly to the combination of weapons and cartridge cases therefor.

An important object of this invention is to reduce the weight of the weapon. Another object is to increase the rate of fire of the weapon by reducing the number of operations necessary to fire a round. Another object is to increase the venturi life in recoilless weapons. Another object is to increase the uniformity of recoil throughout the life of the recoilless rifle. Still another object is to provide a recoilless rifle with automatic ejection of a cartridge case. Still another object is to reduce the number of components in a recoilless Weapon.

According to this invention the breech block may be reduced in weight or in the recoilless rifle, completely eliminated. This is accomplished by having the cartridge case take up some of the load of the conventional breech block, and in the case of the recoilless rifle takes the place of the breech block which forms the inner portion of the venturi.

In order that the invention may be more fully understood and readily carried into practice, it is illustrated, by way of example only, in the accompanying drawings, in which:

FIG. 1 is a longitudinal section of the breech end of a weapon according to the invention, showing the application wherein a venturi is present, and having a round of ammunition loaded into the breech.

FIG. 2 is a longitudinal section of the breech end of a weapon showing the outer surface of the cartridge case engaged with the weapon.

FIG. 3 is a detail sectional view transversely through the axis of the tube extension and cartridge case.

FIG. 4 is a detail sectional view in a plane parallel to the axis of the tube extension and cartridge case and through a section of the cartridge case where no serrations are present.

FIG. 5 is a longitudinal section of the breech end of a weapon illustrating another embodiment of the invention, where the tube wall is extended entirely to the rear of the weapon.

FIG. 6 is a sectional view showing the cartridge case expanded by the pressure of the propellant gases.

FIG. 7 shows the perforation pattern in the cartridge case.

FIG. 8 shows the perforation pattern in the tube wall extension.

FIG. 9 shows a transverse cross-sectional view of a spiral wrapped cartridge case embodiment.

Referring to FIGS. 1, 2, 5 and 6, the projectile 8 and propelling charge 12 are carried in a cartridge case 3, in the rear of which is a primer 13 for igniting the propelling charge. The primer is activated by electrical or mechanical means not shown. The weapon tube 2 extended rearward into the chamber 14 and has on its inner surface serrations or projections and recess type connections or roughness 4, which during firing locks with the coinciding roughness 5 on the cartridge case exterior surface. For illustrative purposes the locking serrations 4 have been shown relatively large. Normally they would be made small in size to allow the elastic properties of the cartridge case to fully retract their serrations to a position Where they would clear the extension 2. An abutment 18 limits loading movement of a cartridge.

In FIG. 1, the cartridge case has perforations 6 for exhausting the gases created by the propelling charge 12 into the chamber and out through the venturi opening 16 formed by the chamber rear end and the rear portion 9 of the cartridge case.

In FIG. 5 the rear end of the tube extension 15 forms the inner surface of the venturi.

'FIGS. 2 and 6 show the case walls expanded and locked with the tube extension walls under the action of the pressure differential caused by the burning propellant.

FIG. 3 shows a transverse cross section through the cartridge case and tube extension showing the generally polygonal shape of the cartridge case 3 where the roughness or threads 5 can expand into the corresponding locking surface 4 shown dotted.

FIG. 4 shows the position where the cartridge case outer surface serrations are interrupted and smooth along the longitudinal vertices 17 of the polygonal side faces, to allow for easy assembly in the weapon and also indicating the surface less than the full circumference which has to be expanded. As shown in the drawing the serrations 5 on the case are of maximum depth in the central longitudinal portion of each side face and gradually diminish in depth to adjacent each edge or longitudinal vertex 17.

FIGS. 5 and 6 show the location of holes in the cartridge case 6 and holes in the tube extension 7 such that the propellant gases may be discharged into the chamber.

FIG. 7 shows the hole pattern in the caseancl the serration or'pin and slot type locating device 10 which fits into the locating device 11 in the tube extension, in FIG. 8 such that the perforations 6 in the case line up with the perforations 7 in the weapon tube extension.

In operation, the primer 13 is activated which ignites the propellant charge 12 creating internal pressure in the cartridge case 3. Under this pressure the case walls expand and lock with the inner surface of the tube extension. The bullet pull of the projectile in the cartridge case is adjusted so that there is no unbalance before the case and tube extension are locked together. Upon the release of the pressure inside the case, the case walls elastically contract and unlock from the tube extension, and the residual propellant pressure ejects the cartridge case from the weapon.

To insure locking of the case wall and tube extension, their mating surfaces are roughened or serrated or have a projection and recess type connection. The case is made generally polygonal in cross section. After roughening or threading, a smooth surface is machined on the surface to permit easy insertion of the round and present less circumferential area, for expansion. Also, the physical properties of the case wall are selected and the serration height adjusted so that the material is not stressed beyond its elastic limit.

With this invention the rate of fire can be increased, as no breech mechanism is needed, and ejection is automatic.

Since the cartridge case forms the inner surface of the venturi essentially a new venturi is fired with each round thus increasing the life of the venturi and providing almost constant recoil throughout the life of the venturi.

I claim:

1. A recoilless weapon comprising a gun tube, a rear portion of said tube having a chamber for reception of a proieetile and a metal case for" propellant, an abutment in said tube for limiting insertion of a case therein, a ven turi passageway leading from around a rear portion of said tube, said venturi passageway having a constricted throat between tapered portions, a single unitary member secured to said tube and constituting a radially outer wall of said venturi passageway and its constricted throat, a metal case in said gun tube containing a propellant and having a rear portion extending beyond said throat and provided with a closed end wall, a portion of said case forward of said constricted throat being perforate for movement of products of propellant combustion into and through said venturi passageway, said tube in rear of said abutment having radially inwardly extending serrations on an inner surface, said case being of a general polygonal cross section and provided with radially outwardly extending serrations on an outer surface for engagement between the serrations of said tube except along the vertices of the side faces of said case where such case serrations are interrupted, said case serrations being of a height to enable sliding of said case into said tube and of maximum height adjacent a central longitudinal portion of each side face and of gradually less height toward each of the bounding vertices of that side face whereby on firing propellant in said case each of the side faces are bulged radially outward to engage its serrations between tube serrations and positively lock the case in said tube, said case being stressed below its elastic limit by internal pressure whereby on reduction in internal pressure said case becomes unlocked from positive engagement with said tube and due tothe cross sectional shape of the case the outward serrations may easily engage the tube serrations to positively lock the case in said tube and on reduction in pressure readily disengage to enable the case to become unlocked from said tube.

2. A weapon according to claim 1 in which the gun tube terminates beforereaching the constricted throat portion of said venturi passageway and the outer surface of said case in rear of said perforate portion functions as an inner wall surface of saidventuri passageway.

3. A weapon according to claim 1 in which the gun tube "and case both extend rearwardly when said case is contiguous to said abutment and said tube is provided with a perforate portion alined with the perforate portion of said case, said tube, case, and outer wall of the venturi wall terminating at about a same plane normal to the tube axis.

4. A metal case for propellant in a recoilless gun, the rear wall of said case being closed for reception therein of a primer, a substantial length of the case outer surface being provided with radially outwardly extending serrations for cooperation with complementary radially inwardly extending serrations in a gun tube, said case between its ends being of general polygonal cross section with said serrations being of maximum depth centrally and longitudinally of each face, each face being bounded by a 1ongitudinal vertex between it and an adjacent face, said outwardly extending serrations on each face being of gradually diminishing depth from a central longitudinal portion of each face to adjacent a longitudinal vertex where said serrations are interrupted and whereby when said longitudinal vertices slidingly fit within complementary serrations in a gun tube the side faces may expand to positively lock said case on firing a propellant and on reduction in internal pressure of a value stressing the case walls below their elastic limit may readily return to their original shape.

References Cited in the file of this patent UNITED STATES PATENTS 39,109 Bakewell July 7, 1863 1,028,358 Johnson June 4, 1912 1,028,430 Burton June 4, 1912 1,123,362 Pedersen Ian. 5, 1915 1,280,579 Stone et a1. Oct. 1, 1918 1,311,021 Spear et a1. July 22, 1919 2,438,297 Pope Mar. 23, 1948 2,598,256 Hickman May 27, 1952 2,651,972 Engelke Sept. 15, 1953 2,919,629 Abramson Jan. 5, 1960 2,925,014 Abramson i Feb. 16, 1960 

